Any systems that work for 1-person campaigns?

So I have my heart set on a text-based campaign but I'm not sure how well it would work with multiple players. I think a 1 person campaign would be perfect for a text-based campaign because then it's just the DM and the player going back and forth. Are there any systems that can accommodate this  without too much hassle? Thanks.

Well, I have two friends who pretty often sit down face-to-face and have DnD3.5-sessions. I'm not entirely sure what they do exactly, except I know they switch around on being GMs and also give each other lots of feedback. But from my understanding they do whole sessions as "normal". Which basically means that there's lots of systems which would make it... Pathfinder too. One way of doing this easily, is by selecting the encounters. If he's Level 2, set him up against one or two Level 1 characters, and so on. But don't rely too much on CR, but more on what's logical :-)  

For a game like that I would use a very descriptive free form rules lite game not a d20 rules set. I would recommend FATE,  roll 20 handles the dice mechanic with /r 4dF and the rules are free. FATE RPG It uses aspects of scenes and characters that you invoke to get modifiers to your rolls, it is hard for me to explain but for those who get into they seem to love the game.

I ran campaigns for 1 player at a time for many years using AD&D 2nd edition. I don't think it is the system itself but more the design of the setting you create, your story line, your particular situations you set up for said character.

Any system can be used to run a 1 player game. As oldschoolchris said. It is more about the setting, storyline, and how you want to run it more than anything else. I've ran 1 player games in od&d, AD&D, GURPS, Star Frontiers, Most of the Palladium systems, and a whole lot more that I can even remember their names. If you feel the need to have more than 1 character then put in a few support npcs to work with the character. As for text based games,I have a live game on wednesday every week that is text based. I run a play by post game here also. The Wed game has 6 players and the pbp game has 6 players.